To be honest, my initial thought was no. However, I thought for a bit and maybe you could. Obviously, you'd have to peel the grip off partially in order to get to the staple to take the butt-cap off but maybe the grip would remain sticky enough to stick back down. If not, you could maybe stick it down with some double-sided tape?

Still, I think that if you're going to remove the butt-cap, you should just replace the grip after you put the butt-cap back on.

I don't think it's possible to do that and leave the grip in any usable condition. Especially after putting it back on once you're done with whatever you're doing to it (adding weight?). Even if you're able to peel the grip back enough to take it off, good luck being able to get it stapled back on with the grip still on there. Just spend the extra $5 and 5 minutes to replace the grip.